Impactor a frame part for an impactor a part to be used in an impactor and a method for processing elements belonging to the impactor

ABSTRACT

An impactor, a frame part for an impactor, a part to be used in an impactor, and a method for processing elements belonging to the impactor. Different elements belonging to different stages of the impactor are coupled to each other with a connecting element in such a way that they can be inserted in the frame part of the impactor, removed from it, or processed, as a single unit.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present invention claims priority from Finnish patent application20012258 filed 21 Nov. 2001 and is the U.S. National Phase under 35U.S.C. §371 of PCT/FI2002/00923 filed 20 Nov. 2002.

FIELD OF THE INVENTION

The invention relates to an impactor, a frame part for an impactor, apart to be used in an impactor, and to a method for processing elementsbelonging to an impactor.

BACKGROUND OF THE INVENTION

With tightening environmental regulations, there is an increasing needfor the measurement of particle emissions. In particular, the need formeasurement is present in the development of filtering methods, in theresearch of various combustion processes, as well as in processes formonitoring actual emissions. In particle measurements, so-called cascadeimpactors have been conventionally used to classify the particlesaccording to the particle size.

FIG. 1 shows a cross-sectional view of an impactor 10 consisting ofseveral stages according to prior art. To simplify the figure, only thefirst two stages have been drawn. The flow 11 to be analyzed is sucked,for example by negative pressure, through the impactor 10. The air flow11 is introduced through the frame structure 15 of the impactor to afirst chamber 19 a. Each stage comprises a nozzle part 12 a; 12 bequipped with orifices which are passed through by the flow carryingparticles. Collection surfaces 13 a; 13 b are placed behind the nozzleparts 12 a; 12 b. The collection surface is provided with at least oneoutlet, through which the flow is allowed to flow to the next chamber orout of the impactor.

FIG. 2 shows a detail of the collection surface 13. The flow directionof the air flow 11 through the orifices of-the nozzle part is abruptlychanged when it impacts upon the collection surface 13. Particles 21carried by the flow 11 and having a sufficiently low mechanical mobilitycannot follow the abrupt change in the direction of the flow but theyhit the collection surface 13. The particles 21 having hit thecollection surface 13 are deposited on the collection surface 13,forming a mass 22.

The mechanical mobility of the particles depends in a known way on theparticle size. This makes it possible to classify the particlesselectively according to the size. By selecting, in a known way, thenumber and size of orifices in the nozzle part 12 a, 12 b shown in FIG.1, the distance between the nozzle part 12 a; 12 b and the collectionsurface 13 a; 13 b, as well as the flow rate to be used, it is possibleto dimension each impactor stage in such a way that only particleshaving a mechanical mobility smaller than a desired value, i.e. beinglarger than a given particle size, are deposited on the collectionsurface 13 a; 13 b at each stage.

The successive stages can be dimensioned so that the first stagecollects the largest particles (for example, particles with a diametergreater than 100 μm), the second stage collects the particles slightlysmaller than these (for example, 10 to 100 μm), and the next stageswould collect smaller and smaller particles, respectively. Thus, bymeasuring the masses 22 deposited on the collection surfaces 13 at thedifferent collecting stages, it is possible to determine the sizedistribution of the particles in the flow under analysis. Inconventional impactors, the mass deposited on the collection surface 13is measured by weighing. In electrical impactors, an estimate of themass deposited on the collection surface is made by monitoring thecurrent caused by electric charges discharged by particles deposited onthe collection surface.

A problem with the above-described impactor of prior art is the amountof work required for removing and reinstalling the collection surfaces.As mentioned earlier, in conventional impactors it is necessary toremove the collection surfaces for weighing; however, in electricalimpactors it is also necessary to remove the collection surfaces,although not for obtaining the measurement result itself, as inconventional impactors. After a given measuring time, both impactortypes require cleaning to remove the mass deposited on the collectionsurfaces. If this were not done, the collection surfaces wouldeventually be filled in such a way that the mass deposited on them wouldeither impair the passage of the flow or, when disengaged, it would becarried to the next stage and cause an error in the measurements. Toreduce this “blow off” effect, as well as the bouncing of particleshitting the collection surface, the collection surface 13 is typicallytreated with a substance which facilitates adhesion.

Both conventional and electrical impactors must be cleaned at regularintervals. Impactors of prior art are constructed in such a way thatthey must be disassembled part by part. For example, to disassemble theimpactor of FIG. 1, first the shielding cover 15 would be removed, thenthe cover part 16 of the first stage and the supporting/shielding part17 a underneath the cover. Next, the nozzle part 12 a of the first stagecan be removed. After the removal of the nozzle part, it is possible toremove the collection surface 13 a. After this, the supporting/shieldingpart 17 b, the nozzle part 12 b and the collection surface 13 b of thesecond stage can be removed, respectively. In a corresponding manner,all the stages of the impactor are gone through. After the disassembly,the removed collection surfaces 13 a, 13 b can be weighed, if necessary.The partly disassembled impactor can then be cleaned, for example byplacing the parts in a separate washing device. After the cleaning, theimpactor is assembled in an order inverse to that presented above, afterwhich the impactor can be used for measuring again.

SUMMARY OF THE INVENTION

As presented above, it is necessary to clean the impactor. However, thedisassembly and assembly of the impactor of prior art is a relativelycomplex and laborious operation. It is an aim of the impactor and theparts intended for use in the impactor, and the processing method, toeliminate the above-described problems of prior art. By means of theinvention, it is possible to remove or install all the collectionsurfaces in the impactor in a single operation, if necessary.

By means of a part according to the invention, the impactor can also becleaned in a simpler and faster way than according to the prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in detail withreference to the appended drawings, in which

FIG. 1 shows an impactor of prior art,

FIG. 2 shows the impingement of particles to be measured on a collectionsurface,

FIG. 3 illustrates an embodiment of the impactor and a part to be usedin the impactor according to the invention,

FIG. 4 illustrates an embodiment of a frame part for the impactoraccording to the invention,

FIG. 5 shows an embodiment of a part to be used for cleaning theimpactor according to the invention,

FIG. 6 shows a second embodiment of the impactor and two parts to beused in the impactor according to the invention,

FIG. 7 shows a third embodiment of a part to be used in the impactoraccording to the invention, and

FIG. 8 shows an embodiment of the processing method according to theinvention.

DETAILED DESCRIPTION OF THE INVENTION

FIGS. 1 and 2 have been discussed above in connection with the priorart.

FIG. 3 shows an embodiment of the impactor according to the invention ina cross-sectional view. The impactor consists of a frame part 31 with aninlet connector 32 a for supplying a flow to be analyzed into theimpactor, and an outlet connector 32 b for discharging the measured flowfrom the impactor. To simplify the drawing, only four stages 33 a 14 33d are shown in FIG. 3, but it will be obvious for a person skilled inthe art that the number of stages in the impactor may vary to a greatextent. In view of the arrangement according to the invention, thenumber of stages in the impactor is not significant as long as it isgreater than one. Each stage is preferably provided with a separatenozzle part 39 a–39 d to provide the desired flow properties.

Furthermore, each stage is provided with a separate collection surface34 a–34 d, on which the particles in the flow under analysis aredeposited, as described above. The shape of the collection surfaces ismainly dependent on the need for measurement. In some measurements, itis advantageous to use cylindrical collection surfaces, in other casesrectangular ones. The arrangement according to the invention does notlimit the geometry used in the collection surfaces, wherein it can beselected according to the respective need.

Each collection surface 34 a–34 d is coupled to a supporting means 35a–35 d. Preferably, the supporting means 35 a–35 d are integrated withrespect to the collection surfaces 34 a–34 d to avoid tolerances causedby extra connections which will complicate the placement of thecollection surfaces 34 a–34 d precisely in the correct position inrelation to the other parts of the stages 33 a–33 d, such as the nozzleparts 39 a–39 d. The placement of the collection surface in the correctposition in relation to the other parts of the stage is important,because the dimensioning of the stage is a factor determining whichparticles are deposited in each stage, as was stated above in thedescription of the prior art. If the collection surface is in anincorrect position, it may cause significant errors in the measurementresults of the impactor.

In an advantageous embodiment, both the collection surface 34 a–34 d andthe supporting means 35 a–35 d are formed by a cylindrical object, forexample a metal tube, inserted in the frame part 31 of the impactor. Inview of the operation of the impactor, it is advantageous to seal theconnection points of the frame part 31 and the supporting means 35 a–35d in such a way that the flow to be analyzed cannot be affected by anundesirable outflow or inflow caused by the through hole. This sealingcan be implemented in a way known as such by a person skilled in theart. The supporting means 35 a–35 d may also have a more complexstructure; i.e., they may consist of, for example, several parts.Furthermore, the arrangement according to the invention does notrestrict the position of the collection surface in relation to thethrough hole, although the figures show, as an advantageous embodimentof the arrangement, an example in which the collection surface isaligned with the through hole and the supporting means 35 a–35 d.

In FIG. 3, the supporting means 35 a–35 d are coupled to each other witha connecting element 36 outside the frame part 31. The connectingelement 36 may be a single solid part, to which the supporting means 35a–35 d are coupled, or the connecting element 36 may consist, as shownin FIG. 3, of several smaller coupling units 37 a–37 c which preferablycouple the supporting parts 35 a–35 d connected to the collectingsurfaces of adjacent stages to each other. The advantage of the solidconnecting element 36 is its simplicity and easy manufacture. In view ofthe control of the device, in turn, it is more advantageous to useseveral coupling units, because the coupling units can be preferablyprovided with control means, e.g. a millimetre screw, by means of whichit is possible to adjust the position of the supporting means coupled toeach other and thereby also the collection surfaces coupled to thesupporting means, in relation to each other and the frame part. This isadvantageous for the adjustment of the impactor.

The connecting element 36 connects the supporting means 35 a–35 d andthe collection surfaces 34 a–35 d further coupled to them to form asingle aggregate, which will be called a combination element in thisapplication, in such a way that said aggregate can be separated as asingle unit from the frame part. Thus, preferably all the collectionplates belonging to the different stages 33 a–33 d of the impactor canbe removed at one time. This provides an obvious advantage to thearrangement of prior art, because the removal and the installation ofall the different collection stages can thus be performed in a singleoperation and does not require that the whole impactor is disassembledinto small parts. In a corresponding manner, also the installation ofthe collection surfaces in the impactor can be implemented in a singleoperation.

On the other hand, the connecting element 36 can be made such that allthe collection stages do not need to be removed together, if desired.For example, the coupling units 37 a–37 c can be made such that, ifnecessary, the coupling units 37 a and 37 b can be removed from thesupporting means 35 b connected to the collection surface 34 b of thesecond stage 33 b in such a way that the collection surface 34 b can beremoved from the frame part 31 without a need to remove the collectionsurfaces of the other stages, or the supporting means coupled to them,from the frame part 31.

The combination element can be preferably implemented in such a way thatsome of the elements connected to it, such as the collection surfaces,can be replaced in a single operation. This is achieved, for example, byconnecting the collection surfaces to the supporting means in such a waythat they can be easily removed, if desired. This makes it possible toreplace and change collection surfaces by removing at least some of thecollection surfaces of the combination element, for example, by means ofa separate element, and by installing new collection surfacesrespectively, several collection surfaces at a time. In an advantageousembodiment, after the measurement, the combination elements are removedfrom the frame part of the impactor and inserted into a separatecollecting part comprising a separate compartment for the collectionsurface of each stage. After this, all the collection surfaces areremoved in a single operation in such a way that they remain in theirrespective compartments within the collecting part. This is preferablyachieved by providing the combination element with a separate lockingmeans, by which all the collection plates are released or locked againstthe supporting means, respectively.

After the removal of old collection surfaces, the combination element iscleaned and the new collection surfaces are installed from a part forinserting collection surfaces, provided with a separate compartment foreach new collection surface. The combination element is inserted in theinserting part in such a way that each supporting means is connected tothe respective collection surface. In this way, all the collectionsurfaces can be installed in a single operation and it will not benecessary to install each collection surface separately as in thearrangement of prior art.

FIG. 4 shows a frame part 31 for an impactor according to the invention,as well as a cross-sectional view along the line A—A of the frame part.The frame part 31 is provided with lead-through provisions, for exampleby drilling holes 41 in the frame part 31. These through holes make itpossible to insert various elements in the frame part 31. Such elementsmay include, for example, the above-described collection surfaces 34a–34 d, cleaning means to be described below, or nozzle parts. Theinvention makes it possible to provide an arrangement, in which theframe part 31 may, if necessary, consist of a single piece, because theinsertion or removal of the elements does not require the disassembly ofthe frame part. Naturally, the frame part may also consist of severalpieces, wherein the advantage of the invention is clearly manifested.The elements can be handled and adjusted without a need to disassemblethe impactor.

FIG. 5 shows an auxiliary device 50 according to the invention, intendedto be used in connection with the impactor for its cleaning. The device50 comprises nozzle parts 51 a–51 d to be inserted in the frame part 31,provided with holes 59 to introduce a substance used for cleaning,preferably hot water vapour, into the frame. The basic structure of thedevice corresponds to the structure already presented above inconnection with FIG. 3; that is, the device comprises a connectingelement 56, by means of which nozzle parts 51 a–51 d intended forseveral different stages can be inserted in the frame part 31 or removedfrom it as a single unit.

The device 50 is also provided with a connector 52 for feeding asubstance to be used for cleaning, from a source 53 to the device 50.The dispensing of the substance inside the device 50, from the connector52 to the nozzle parts 51 a–51 d, can be implemented in a way known assuch for a person skilled in the art.

FIG. 6 shows a second advantageous embodiment of the above-describedbasic arrangement according to the invention. In addition to the element61 connecting the collection surfaces of the different stages, asdescribed above in connection with FIG. 3, and the frame part 31, asecond combination element 62 is also shown in FIG. 6. The basicstructure of the second combination element 62 is similar to that of thefirst combination element 61 with the difference that the secondcombination element does not comprise the collection surfaces of thestages but, for example, the nozzle parts of the different stages and/orother parts needed in the structures of the stages. Preferably, thestructure of the second combination element may be such that itcomprises all the elements needed in the stage, except for thecollection surfaces.

If the structure of the impactor according to the invention isimplemented according to FIG. 6, in which the first and the secondcombination elements 61 and 62 are inserted into the frame part fromopposite sides, the frame part 31 must naturally be provided with twosets of through holes, one for the first combination element 61 and theother for the second combination element 62. The structure can also beimplemented in such a way that both the combination elements areinserted from the same side, wherein the alternatives are to make twosets of through holes on the same side or to install both of thecombination elements in the same through holes. The latter alternativecould be implemented, for example, in such a way that the secondcombination element 62 is first installed in its position, after whichthe first combination element 61 is inserted in the second combinationelement 62, as shown in FIG. 7. It will be obvious for a person skilledin the art that the mutual order of connecting the first and secondcombination elements 61 and 62, as well as the order of connecting themin the frame part, can also be different from that presented above. Forexample, the first combination element 61 can be connected to the secondcombination element 62 first, after which the unit thus formed isinserted in the frame part 31.

The above-described elements, intended for use in the impactor, can bepreferably processed by the following method, which belongs to the scopeof the same inventive idea as the above-described impactor, frame partfor the impactor, and parts intended for use in the impactor. In themethod, the part to be used in the impactor, comprising elementsintended for different stages of the impactor, preferably collectionsurfaces or nozzle parts, are processed in such a way that at least someof the different elements are processed simultaneously in differentprocesses.

FIG. 8 shows an embodiment of the method according to the invention. InFIG. 8, the combination element 61 is inserted in a cleaning part 80which comprises a separate cleaning solution 81 a–81 c for eachcollection surface 34 a–34 c. The collection surfaces 34 a–34 c arefixed to the combination element 61, wherein a single operation will besufficient to set them for processing. Because each collection surface34 a–34 c is provided with a separate cleaning solution, cleaningliquids of different concentrations can be used for different collectionsurfaces simultaneously. This makes it possible, for example, to subjectthe most soiled collection surfaces to stronger cleaning processes,preferably a stronger cleaning solution, than the less soiled collectionsurfaces, without operations involved in the removal of the surfaces.

In addition to the above-described cleaning process, the method is alsosuitable for other processing related to the combination element, suchas, for example, the coating of the elements, greasing, or otherprocesses to reduce undesirable effects.

Hereinabove, some embodiments of the impactor and the parts to be usedin the impactor according to the invention have been described indetail; however, the invention is not restricted solely to theseembodiments, but it may vary within the scope of the appended claims. Inparticular, the term impactor must not be interpreted as a restrictionto any given impactor type. The basic idea of the invention will work aslong as the impactor comprises more than one stage. Thus, it will beobvious for a person skilled in the art that the invention can beutilized in, but is not restricted solely to, for example, cascadeimpactors, electrical impactors, such as electrical low pressureimpactors, or virtual impactors.

1. An electrical impactor, comprising: at least two impactor stages,each stage comprising a nozzle part and a collection surface and asupport to which at least one of the collection surface or the nozzlepart is operatively connected; a connecting element operativelyconnected to the support; and a frame part enclosing the at least twoimpactor stages, wherein said connecting element is arranged such thatat least one element one of the nozzle part or the collection surfacecan be introduced in and/or removed from said impactor stages arrangedin the frame part as a single unit.
 2. The impactor according to claim1, wherein said nozzle part is used for cleaning the impactor stage. 3.The impactor according to claim 1, wherein said connecting elementcomprises at least one coupling unit.
 4. The impactor according to claim3, wherein said coupling unit allows the adjustment of a single elementwithout affecting the other elements coupled to said connecting element.5. The impactor according to claim 4, wherein said coupling unit allowsthe removal of one of the nozzle part or the collection surface fromsaid frame part or its insertion in said frame part without affectingother elements coupled to said connecting element.
 6. A frame part foran electrical impactor comprising several stages, wherein said framepart enclosing the at least two impactor stages includes holes forallowing the insertion of at least two elements belonging to differentstages in said frame part and/or their removal from said frame part as asingle unit.
 7. The frame part according to claim 6, wherein saidseveral elements are the collecting surfaces of at least two differentstages.
 8. The frame part according to claim 6, wherein said severalelements are the nozzle parts used for cleaning the impactor stages. 9.A combination element to be used in an electrical impactor whichimpactor comprises a frame part enclosing at least two impactor stages,wherein each of the stages comprises at least one element, wherein saidcombination element comprises: at least one supporting means, at leasttwo elements each having one of the supporting means coupled thereto, aconnecting element having one of the supporting means coupled thereto,wherein said at least two elements belonging to at least two stages canbe introduced in and/or removed from said impactor stages arranged inthe frame part as a single unit.
 10. The combination element accordingto claim 9, wherein said element is a collecting surface.
 11. Thecombination element according to claim 9, wherein said element is anozzle part used for cleaning the impactor.
 12. The combination elementaccording to claim 9, wherein said element comprises outlets forfunnelling a cleaning agent to the impactor stage.
 13. The combinationelement according to claim 12, wherein said cleaning agent comprises hotwater vapor.
 14. The combination element according to claim 9, whereinsaid connecting element comprises at least one coupling unit.
 15. Thecombination element according to claim 14, wherein said at least onecoupling unit allows the adjustment of a single element withoutaffecting the other elements coupled to said connecting element.
 16. Thecombination element according to claim 15, wherein said coupling unitallows the removal of a single element from said frame part or itsinsertion in said frame part without affecting the other elementscoupled to said connecting element.